Get over it.
It's like saying a big business would waste 5-6million because it helps the smaller businesses.. It doesn't work like that. If there is a way to save money, you save it.
If you have agreed on something and you are called to honor the agreement then you just do it . No problem trying to mitigate the costs, but doing the deal so that other club get's nothing is purely bad faith and this will affect Southampton in future and might cost them in long run more than what they save.